U.S. Pat. No. 3,698,943 to Colantuono discloses a protective coating for high-speed tool steel billets. The coating protects against oxidation and includes sodium borate, silica, and alumina. Weldes et al U.S. Pat. No. 3,372,038 discloses a corrosion-resistant metal coating having aluminum powder dispersed in organic ammonium silicate.
Gedwill et al U.S. Pat. Nos. 3,849,865 and 3,869,779 disclose coatings in which a ductile oxidation resistant metallic alloy is initially applied to a superalloy. An aluminide coating is then applied to the metallic alloy.
Stecura et al U.S. Pat. No. 4,055,705 is directed to a thermal barrier coating system comprising a NiCrAlY bond coating and a reflective oxide thermal barrier coating. The reflective oxide is preferably zirconia that is stabilized with another oxide.